Folding stairway



Dec. 3, 1957 P. v. HARMON ,8 59

FOLDING STAiRWAY Filed March 31, 1952 '2 She'ets-Sheet l INVENTOR PAUL.l/ HAFEMUN ATTORNEY Dec. 3, 1957 v. HARMON 2,815,159

FOLDING STAIRWAY Filed March 31, 1952 v 2 Sheets-Sheet 2 INVENTOR R4041/. HAHMoN' ATTORNEY Patented Dec. 3, 1957 ice FOLDING STAIRWAY Paul V.Harmon, Nashville, Tenn., assignor to Precision Parts Corporation,Nashvilie, Tenn., a corporation of Tennessee Application March 31, 1952,Serial No. 279,581

6 Claims. (Cl. 228-50) This invention relates to folding stairways andis a continuation in part of my co-pending application Serial No.751,107 filed May 28, 1947, now abandoned.

Folding stairways are in more or less common use for providingconvenient access to attics without requiring the space occupied bypermanent stairs. Folding stairs are movable to upper inoperativepositions within a frame fixed in the ceiling and usually arecounterbalanced to remain in such normal position by spring means.

While spring counterbalancing means are fully operative and practicablethey possess several definite disadvantages. tn the first place they arerelatively expensive to manufacture and the springs sometimes break dueto crystallization of the metal. Moreover, spring devices used for thispurpose are loaded to the maximum extent when the stairway is unfoldedand to the minimum extent when the stairway is in the folded inoperativeposition. Spring counterbalanced folding stairways some years agosuperseded the original stairways of this type wherein the stairway wasrigid from end to end and substantially longer than the frame mounted inthe ceiling. It was the common practice to slide such stairways upwardlyendwise thereof and then to swing the lower end of the stairway about ahorizontal rocking axis to move the stairway to inoperative position.The upper end of such stairway counterbalanced the lower end thereof andthus held the stairway folded, but the end of the stairway acting as thecounterbalance occupied substantial attic floor space which had to bekept clear in order for the stairway to fold. This objection is overcomeby the spring counterbalancing devices now in common use but thesedevices are disadvantageous for many reasons, several of which have beenmentioned above.

An important object of the present invention is to provide a foldingstairway in which counterbalancing spring devices are completelyeliminated and the stairway is counterweighted to be held in folded orinoperative position without requiring any free floor space in theattic, the entire stairway and its counterbalancing means being retainedwholly or substantially wholly within the limits of the ceiling frame.

A further object is to provide such a stairway wherein a simple type ofcounterweighting means is employed and wherein such means provideslittle or no counterweighting action when the stairway is unfolded butprovides the maximum counterbalancing forces when the stairway isfolded, this being the condition in which maximum counterweighting isdesired.

A further object is to provide such a stairway which can be movedbetween folded and unfolded positions with a minimum amount of effort,thus rendering the stairway operative by a small child, the forcenecessary for swinging the structure between its two positions beingmaterially reduced by a highly simple but effective antifriction bearingmeans.

A further object is to provide such a structure wherein thecounterweighting means substantially overbalances the stairway as thefolded positions of the parts are approached and wherein the stairstructure substantially overbalances the counterweighting means as thestair structure approaches the unfolded positions of the parts, thusproviding a high degree of stability of the parts in either of the twopositions referred to.

A further object is to provide a folding stairway of the characterreferred to wherein the substantial overbalancing of the parts in thetwo positions referred to and the extreme ease of movement of the partstends to cause the ladder to swing too rapidly toward either limit ofmovement, and to provide in conjunction with the structure a novel typeof dash pot control means to tend to retard movement of the parts asthey approach either limit of movement while providing relativelyunrestricted movement of the parts away from the two positions referredto and intermediate such positions.

Other objects and advantages of the invention will become apparentduring the course of the following description. In the drawings I haveshown one embodiment of the invention. In this showing:

Fig. 1 is a perspective View of the stairway showing the parts in solidlines in the fully unfolded operative positions of the parts with two ofthe stair sections shown partly folded in dotted lines;

Fig. 2 is a vertical longitudinal sectional view through the structureshowing the parts in the fully closed or folded positions;

Fig. 3 is a transverse vertical sectional view taken substantially online 33 of Fig. 2;

Fig. 4 is an enlarged fragmentary side elevation of a supporting bracketand associated elements showing in section the dash pot associatedtherewith;

Fig. 5 is an enlarged fragmentary side elevation, at a smaller scalethan Fig. 4, showing one of the counterweight levers and associatedparts, a portion of the lever arm being broken away;

Fig. 6 is a section of line 6-6 of Fig. 5, parts being shown inelevation;

Fig. 7 is an enlarged detailed sectional view on line 77 of Fig. 6; and

Fig. 8 is a fragmentary perspective view of one of the abutment stopsand associated elements.

Referring to Fig. 1, the numeral 10 designates as a whole a ceilingframe comprising vertically arranged longitudinal side frame members 11and similarly arran ed end frame members 12 defining an access opening13. The lower edge of the frame is provided with strips forming arectangular trim 14 which lies against the ceiling of a hall or roomwith the frame 10 projecting upwardly therethrough with its upper edgesubstantially flush with the floor above. The opening 13 is normallyclosed by a panel 16 hinged to the frame 10 as at 17. The panel 16preferably is transversely braced by means of batten strips 18.

The structure further comprises a plurality of ladder or stair sectionsrespectively indicated by the numerals 20, 21 and 22 each of whichcomprises spaced side rails 23 connected by steps or rungs 24equidistantly spaced to form a stairway when the parts are fullyunfolded as shown in solid lines in Fig. l. The stair section 2% is thelongest of the three sections, being almost co-extensive in length withthe panel 16, and the side rails 23 of such section are fixed to thestrips 18 in any suitable manner, as will be apparent. The side rails ofthe stair sections 21) and 21 are hinged to each other at the top edgesthereof when the sections are unfolded, as indicated by the numeral 26The lower edges of the sections 21 and 22 are hinged to each other as at27, thus permitting the sections 21 and 22 to be swung upwardly inhinged relation to each other and to the section 20, as suggested indotted lines in Fig. 1, to assume the fully folded positions shown inFig. 2. Each of the step members 24 is provided with an antiskid treadmember 28 which may be formed of rubber or any other suitable material.

A hand rail 30 is preferably provided for the stair section 20, thisrail being connected to one of the side rails 23 of the section 20 byposts or the like 31.

Novel means is provided for counterbalancing the stair structuredescribed, to hold the latter in the fully folded position shown in Fig.2. Each longitudinal frame member 11 carries fixed thereto as at 34 aplate 35 forming part of a bearing casting projecting substantiallyabove the frame 10. Each plate 35 at its upper end carries a cylindricalbearing 36. The bearings of the two plates 35 obviously are arranged inaxial alignment. The two bearings are identical and project outwardly ofthe plates 35 as clearly shown in Figs. 3 and 6.

A counterbalancing lever indicated as a whole by the numeral 37 isassociated with each bearing 36, the two levers 37 being identical witheach other. Each lever 37 comprises a lower casting 38, which may bemade conveniently and economically of aluminum, and this casting has acircular lower end 39 overlying one end of one of the bearings 36, asshown in Fig. 6. Each casting 38 carries a laterally projecting trunnion40 extending through the associated bearing 36. Each trunnion is smallerin diameter than the internal diameter of the associated bearing toprovide an annular space 41 (Fig. 7) in which is arranged a plurality ofneedle or roller bearings 47.. These bearings are simply sections of acircular rod suitably cut to length and each has one end abutting thecircular end 39 of the associated counterweight lever.

At the inner face of each bearing 36 is arranged the circular end 45 ofan arm 46 and receiving a reduced tapered end 47 of the trunnion 40. Thebody of the trunnion terminates preferably very slightly beyond theplane of the inner face of the bearing 36 to permit the arm 46 to beclamped against the trunnion by a nut 48 without causing the arm 46 tobind against the bearing 36. The circular end 45 of the arm 46 isadapted to abut the adjacent ends of the bearings 42. It will beapparent that the bearings 42 may be made very economically and requireno keepers since the hearings are retained in position by the members 39and 45. In view of the fact that the stair structure as a whole merelyrocks but does not rotate, and ordinarily is operated only occasionally,it is not necessary that the bearings be made of hardened steel or thatthey be associated with perfectly machined surfaces. The provision ofthe bearings, therefore, is economical and an important addition to thestructure since it permits it to swing with extreme ease and freedombetween its two positions.

Each casting 38 acts as a socket to receive one end of a rod or leverarm 50 as shown in Fig. 6, a set screw 51 preferably being provided tofix the elements 38 and 50 with respect to each other. The end of eachrod or arm 50 carries a counterweight element 52 which may be of anysuitable form or material. It has been found highly effective andeconomical to mold the counterweights 50 of cement directly on the freeends of the arms 50.

Each arm 46 has fixed thereto, as at 55, an arm 56 projecting in theopposite direction with respect to the trunnion 40 from thecounterweight 52. Obviously an arm 56 is connected to each arm 46 andthe remote end of each arm 56 is pivotally connected, as at 57, to oneend of a link 58. The other end of each link 58 is pivotally connected,as at 59, to one of the side frame members 23 of the stair section 20.From the foregoing description it will be apparent that eachcounterweight arm 37, its trunnion 40 and arms 46 and 56 form a rigidunit which swings about the axis of the associated trunnion 40.

The inner face of each side frame member 11 carries a plate 62 to whichis fixed an abutment stop 63 preferably formed of resilient material.The plates 62 are preferably 4 secured in position after installation ofthe device in such positions that the abutment stops 63 contact with thearms 58, as shown in Fig. 1, when the stair sections 20, 21 and 22 arein alignment with each other.

In order to control the movements of the parts described above, a noveltype of dash pot indicated as a whole by the numeral 66 is employed,preferably in conjunction with each counterbalancing structure.Referring to Fig. 4, the circular end 39 of each counterweight arm isprovided with a radially extending lug 67, preferably adjacent the innerface of the circular portion 39 as shown in Fig. 3. The lug 67 ispivotally connected by a bolt 68 to the upper end of a plunger rod 69carrying the plunger 70 reciprocable in a cylinder 71. This cylinder atits lower end, and preferably in close proximity to the adjacent plate35, is provided with a lug 72. A bolt 73 passes through this lug andthrough the adjacent plate 35, the latter preferably being provided withan integral pad 74 projecting outwardly from the plate to engage theinner face of the lug 72.

The cylinder 71 is closed at one end, as at 76, and is provided with acap 77 at its other end apertured for the passage therethrough of therod 69. The plunger 70 comprises a pair of sealing cups 78 clampedtogether by plates 79 suitably mounted on the rod 69 and provided withsmall bleed openings 80 affording restricted communication at all timesbetween the cylinder spaces on opposite sides of the plunger 70.Intermediate its ends, the cylinder 71 is provided with one or moreopenings 81. Preferably a plurality of such openings is employed,circumferentially spaced around the cylinder, and affording relativelyfree communication between the atmosphere and one end of the interior ofthe cylinder 71 when the openings 81 are not covered by the plunger 70.The purpose of this arrangement will be described below.

Operation The parts normally occupy the folded positions shown in Fig. 2and it will be noted that the bottom of the panel 16 is flush with thelower face of the trim 14. The surfaces of these elements are preferablysmooth and when finished to correspond to the ceiling of the room, thestructure is hardly visible. It also will be noted in Fig. 2 that all ofthe operating parts of the structure lie wholly within the limits of theframe 10. Referring to Fig. 3, it will be noted that the counterweights52 project only slightly beyond the transverse limits of the frame 10and and trim 14. In some installations slightly longer counterweightarms 37 are required, in which case the counterweights will project veryslightly beyond the cross members 12. In no case, however, is there anysubstantial protrusion of any of the parts beyond the limits of theframe 10 either longitudinally or transversely thereof and, accordingly,the structure does not occupy any attic floor space, which is highlydisadvantageous.

The stair structure readily may be opened for use by pulling downwardlyon the free end of the panel 16. A chain or pull cord (not shown), whichis of course conventional, conveniently may be connected to the free endof the panel 16. The panel is swung downwardly until it occupies theposition shown in Fig. l, at which point the arms 56 will be broughtinto engagement with the abutment stops 63 to limit further movement ofthe counterbalancing means and all of the elements connected thereto. Itwill be noted that the links 58 and their associated arms 56 arearranged only at relatively slight angles with respect to each otherand, accordingly, the

component of force acting horizontally against the abutment stops 63 isminimized. As a matter of fact in many installations the arms 56 andlinks 58 are even more nearly in alignment to further minimizehorizontal com- .ponents of force against the stops 63. Therefore, thereis no great force exerted against these stops when the stairway is inuse and by using resilient elements 63, the structure reaches its openedposition noiselessly.

The structure having been opened in the manner described, the operatorwill then proceed to unfold the stair sections 21 and 22 by reaching upand grasping a step of the section 22 or the side rails thereof andpulling outwardly away from the main stair section 20. The sections 21and 22 are then lowered to the solid line positions shown in Fig. 1, andthe stairway is ready for use. The operations referred to are obviouslyreversed to fold or close the stairway, it merely being necessary tofold the sections 21 and 22 back upon the section 20 and then to pushupwardly on the free end of the panel 16. In this connection it will benoted that while the angle between the arms 56 and links 58 is minimizedfor the purpose stated, it is preferable to preserve a slight angularityto prevent approaching a deadcentering of the various pivot axes.Dead-centering would not actually occur even with alignment of the arms56 and links 58 because of the offsetting of the axes of the trunnions4% from the axes of the pivot members 57 and 59, but slightly greaterforce would be required to close the structure than is true with thearrangement shown.

It will be apparent that the counterweight arms have their greatestmoment in the region of the closed position of the parts shown in Fig.2, and accordingly the counterweights are most effective for holding thestairway in closed position. On the other hand, the most effectivemoment of the stair structure is in the region of the open position ofthe parts since under such conditions the moments of the counterweightlevers are negligible, since these levers are in the nearly verticalpositions shown in solid lines in Figs. 1 and 5. Therefore the structureis very greatly overbalanced and biased to remain in either of its twopositions.

The bearings 4-2, as stated, provide a simple and highly economicalantifriction means for minimizing the effort required to swing the stairstructure between its two positions. This means is so eifective that avery small child can operate the stairway between its two positionswithout assistance. Simple rod sections are employed for the bearings 42and no keepers or retainers are necessary since the ends of the bearingrollers abut the members 39 and 45. In the assembling of the parts, eachtrunnion is inserted in its bearing 36, the bearing rollers are insertedin position, and the circular portion 45 of the arm 46 is slipped overthe tapered end 47 and the nut 48 is applied and tightened. The arm end45 binds on the tapered trunnion section 47 and preferably also bindsagainst the adjacent shoulder of the trunnion 40 without binding againstthe bearing 36.

As stated, the antifriction rollers materially increase the degree ofease with which the stair structure is swung between its two positions.As a matter of fact, this degree of ease is so great that it may bedisadvantageous. As stated, the counterweights greatly overbalance thestair structure in the closed position and as the panel 16 is pulleddownwardly the counterweights 52 swing upwardly and their effectivemoment arms progressively decrease and at an intermediate position ofthe parts the counterweights and stair structure balance each other.During this intermediate range of movement the momentum of the parts maymaterially increase if a substantial force has been applied to the panel16 in pulling it downwardly. This generates a substantial inertia whichcarries the parts too rapidly to the fully opened position and the arms56 will strike the abutment stops 63 with substantial force. Conversely,the closing of the structure, if performed with substantial force, willgenerate inertia in the intermediate positions of the parts which willcarry them too rapidly to closed position and the sudden stopping of theparts in the closed position may strain the parts and cause substantialnoise. The distinct advantage of the antifriction bearings is retainedwhile eliminating the possible disadvantage thereof by providing thedash pots 66. Referring to Fig. 4 in which the parts are shown in theopen position of the stairway, the plunger 70 is at the lower end of itsstroke.

The upper end of the cylinder 71 is open to the atmosphere through theports 81. When the closing movement of the stairway is performed, thecircular member 39 rotates counterclockwise as viewed in Fig. 4 and theplunger 70 moves upwardly and this movement is quite free due to thepresence of the ports 81. In an intermediate position of the parts, theplunger 70 will close the ports 81 at the upper end of the cylinder 71,thus trapping air therein and this air can escape only through the bleedports into the cylinder 71 beneath the plunger. If movement of the partsis quite rapid, the restricted flow of air through the plunger ports 30will build up substantial pressure in the upper end of the cylinder 71thus cushioning the movement of the parts. The inertia of the parts willcarry the plunger 70 beyond the ports 81 and there will be a progressivebuilding up of pressure in the upper end of the cylinder 71 as theeffective moments of the stair parts decrease while the moments of thecounterweight arms increase. This building up of pressure retardsmovement of the parts as the latter approach the fully closed position.

As stated, the same inertia conditions will be present in both theopening and closing movements of the stairway. The dash pots 66 operatein the same manner in both movements of the parts. As the stairisopened, the moments of the stair parts swinging downwardly relativelyincrease as the moments of the counterweight arms decrease, and duringsuch time the plunger 70 will be moving downwardly from the top of thecylinder 71. At an intermediate point, the ports 81 will be closed tothe lower end of the cylinder 71 and pressure will be built up thereinto an extent depending on the speed of movement of the parts. Ifmovement is too rapid, air cannot escape through openings 80 withsuflicient rapidity to maintain atmospheric pressure in the lower end ofthe cylinder 71. and the increase in pressure will retard the movementof the parts and thus prevent the stair structure from reaching the openposition at too great a speed of movement.

Thus it will be apparent that the simple bearing means employed providesfor an extremely free movement of the parts. If this movement takesplace relatively slowly or is manually retarded in the last portion ofthe travel, the dash pots will remain substantially ineffective forretarding the movement of the parts. The dash pots therefore actautomatically only when the speed of movement of the parts is too great,to prevent the parts from reaching either open or closed position at toogreat a speed of movement.

As previously stated, there is substantial over-balancing of the partsin either of the positions thereof and since the counterbalancing elfectof the counterweights is substantially negligible when the stairway isin use, the stair structure may be made as light as structuralrequirements permit. For example, the stairway may be made of magnesiumor aluminum and regardless of the lightness of its weight, it willremain in open position.

The structure employs the simplicity of counterbalancing without thedisadvantage of earlier folding stair structures wherein substantialattic space had to remain free to accommodate one end of the ladder. Thestructure also eliminates the substantial disadvantages incident to theuse of counterbalancing springs, there being no springs of any kindemployed with the structure.

I claim:

1. A folding stairway comprising a generally rectangular open frameadapted to be mounted in a ceiling, a plurality of ladder sectionshinged end to end to swing to operative positions in alignment with eachother and to inoperative positions folded and superimposed relative toeach other, one of said ladder sections being hinged to said frame, abracket fixed to each side of said frame intermediate the ends thereofand projecting substantially thereabove, the upper ends of said bracketsbeing provided with aligned bearings, a lever provided intermediate itsends with a trunnion mounted in each bearing, one end of each leverhaving a counterweight, a link pivotally connected at one end to theother end of each lever and having its opposite end pivotally connectedto one side of said one ladder section at a point remote from the hingedconnection thereof with said frame, said ladder sections being mountedto swing, when folded, to an upper inoperative position within saidframe and to a lower operative position, when said sections areunfolded, said counterweights, when said ladder sections are in theirlower operative positions, projecting upwardly from said bearings toprovide negligible moment arms tending to turn said levers, saidcounterweights, when said ladder sections are in said inoperativepositions, projecting to positions adjacent one end of said frame toexert substantially their maximum moment arms to tend to hold saidladder sections in closed positions, and a dash pot comprising acylinder and a single plunger therein forming a pair of elements one ofwhich is connected to a fixed pivot carried by one of said brackets andthe other of which is pivotally connected to one of said leverseccentrically of its trunnion, said cylinder intermediate its ends beingvented to the atmosphere whereby said plunger is freely relativelymovable in said cylinder away from either end thereof and retarded inits movement as it approaches either end of said cylinder.

2. A folding stairway comprising a generally rectangular open frameadapted to be mounted in a ceiling, a ladder structure pivotallyconnected to said frame at one end thereof to swing between an upperinoperative position and a lower operative position a bracket fixed toeach side of said frame intermediate the ends thereof, said bracketsprojecting substantially above said frame and being provided at theirupper ends with aligned bearings, a pair of levers each providedintermediate its ends with a trunnion rotatable in one of said bearings,one end of each lever being arranged outwardly of its associated bearingand being provided on its end with a counterweight, the other end ofeach lever lying within its associated bearing, and a link connected atone end to said other end of each of said levers, said links beingpivotally connected at their other ends to said ladder structure atpoints remote from the pivotal connection of said ladder structure withsaid frame, said one end of each lever, when said ladder structure is inits upper inoperative position, extending in proximity to but notsubstantially beyond one end of said frame to provide substantiallymaximum moment arms tending to hold said stair structure in suchposition, said counterweights being substantially above said bearingswhen said ladder structure is in its lower operative position wherebythe moment arm of said one end of each lever is substantially negligiblewhen said ladder sections are in such position, said counterweightsbeing movable in vertical planes adjacent but wholly outwardly of thesides of said frame.

3. A folding stairway comprising a generally rectangular open frameadapted to be mounted in a ceiling, a ladder structure pivotallyconnected to said frame at one end thereof to swing between an upperinoperative position and a lower operative position, a bracket fixed toeach side of said frame intermediate the ends thereof, said bracketsprojecting substantially above said frame and being provided at theirupper ends with aligned bearings, a pair of levers each providedintermediate its ends with a trunnion rotatable in one of said bearings,one end of each lever being arranged outwardly of its associated bearingand being provided on its end with a counterweight, the other end ofeach lever lying within its associated bearing, a link connected at oneend to said other end of each of said levers, said links being pivotallyconnected at their other ends to said ladder structure at points remotefrom the pivotal connection of said ladder structure with said frame,said one end of each lever, when said ladder structure is in its upperinoperative position, extending in proximity to but not substantiallybeyond one end of said frame to provide substantially maximum momentarms tending to hold said stair structure in such position, saidcounterweights being substantially above said bearings when said ladderstructure is in its lower operative position whereby the moment arm ofsaid one end of each lever is substantially negligible when said laddersections are in such position, said counterweights being movable invertical planes adjacent but wholly outwardly of the sides of saidframe, and a dash pot comprising a cylinder and a single piston forminga pair of elements one of which is pivoted to a fixed point and theother of which is pivoted to one of said levers eccentrically of itstrunnion, said cylinder intermediate its ends being vented to theatmosphere whereby said piston is movable relatively freely in saidcylinder away from either end thereof, said piston being apertured toafford restricted communication between opposite ends of said cylinderwhereby said piston is free to approach either end of said cylinder ifmoved relatively slowly but is cushioned in such movement if movedrelatively rapidly.

4. A folding stairway comprising a generally rectangular open frameadapted to be mounted in a ceiling, a ladder structure pivotallyconnected at one end to one end of said frame to swing between an upperinoperative position and a lower operative position, a bracket carriedby each side of said frame intermediate the ends thereof and projectingsubstantially above said frame, said brackets being provided at theirupper ends with aligned bearings, a pair of levers each providedintermediate its ends with a trunnion mounted in one of said bearings,each lever having one end arranged outwardly of and in contact with theouter end of one bearing and having its other end in contact with theinner end of such bearing, a counterweight connected to said one end ofeach lever, a link pivotally connected at one end to said other end ofeach lever, said links being pivotally connected at their other ends tosaid ladder structure, said one end of each lever projecting upwardlyfrom its associated bearing when said ladder structure is in itsoperative position and projecting approximately horizontally from suchbearing when said ladder structure is in its inoperative position, and apair of dash pots arranged adjacent and outwardly of opposite sides ofsaid frame, each dash pot comprising an upstanding cylinder pivotallyconnected at its lower end to one of said brackets and a piston in saidcylinder pivotally connected at its upper end to said one arm of theassociated lever eccentric to the trunnion thereof, said cylinderintermediate its ends being vented to the atmosphere whereby said pistonis freely movable away from either end of said cylinder but is cushionedin its approach toward either end of said cylinder.

5. A folding stairway comprising a generally rectangular open frameadapted to be mounted in a ceiling and having end and side walls, aladder structure hinged at one end to said frame adjacent the bottom ofone end wall thereof to swing upwardly to an inoperative position withinsaid frame and downwardly to assume an operative position, bracketsfixed to the said side walls of said frame intermediate the ends thereofand projecting upwardly therefrom, horizontal bearings carried by therespective upper ends of said brackets and having a common axis, atrunnion mounted in each bearing, a lever arm fixed at one end to eachtrunnion adjacent the outer end thereof, a counterweight carried by theother end of each lever arm, said lever arms and their counterweightslying wholly outwardly of the vertical planes of the side walls of saidframe and having their counterweighted ends terminating adjacent saidone end wall, an operating arm fixed to each trunnion at the inner endof its associated bearing and projecting generally toward the other endof said frame when said ladder structure is in inoperative position, andlinks connected between said operating arms and said ladder structure,each operating arm and its associated link lying between one .of saidside walls and the adjacent side of said ladder structure.

6. A folding stairway comprising a rectangular open frame havingelongated parallel side frame members lying in parallel vertical planes,a plurality of ladder sections hinged end to end to swing to operativepositions in alignment with each other and to folded inoperativesuperimposed positions, one of said ladder sections being hinged at oneend thereof to one end of said frame, a bracket fixed to each side framemember intermediate the ends thereof and projecting thereabove andprovided in their upper ends with aligned bearings, a lever providedintermediate its ends with a trunnion mounted in each bearing, one endof each lever being arranged wholly outwardly of its associated bearingand provided with a counterweight, the other end of each lever beingpositioned in a vertical plane adjacent and parallel to the verticalplane of the inner face of the associated side frame member, a linkpivotally connected at one end to the free end of said other end of eachlever inwardly thereof, each link having its other end pivotallyconnected to said one ladder section outwardly thereof at a point remotefrom the pivotal connection thereof with said frame, said counterweightslying outwardly of the outer faces of said frame members to swing invertical planes free of such frame members and to assume positionssubstantially above said bearings when said ladder sections are inalignment and swung downwardly to operative positions, and stops fixedto the inner faces of said frame members and engageable respectivelywith said other lever ends when said ladder sections are swungdownwardly to operative positions to limit movement of said levers andof their pivotal connections with said links whereby the latter serve assupporting means to limit downward movement of said one ladder section.

References Cited in the file of this patent UNITED STATES PATENTS612,156 Chamberlin Oct. 11, 1898 621,669 Hinds Mar. 21, 1899 1,005,201Gurney Oct. 10, 1911 1,346,787 Kryl July 13, 1920 1,457,907 Heisler June5, 1923 1,700,904 Marschke Feb. 5, 1929 2,050,593 Traut Aug. 11, 1936FOREIGN PATENTS 184,218 Switzerland Aug. 1, 1936 496,612 Great BritainDec. 12, 1938 OTHER REFERENCES Popular Science, pg. 215, June 1948.

